Communication system

ABSTRACT

An audio signal and a selected one of a plurality of sub-audio tones are transmitted to a plurality of receiving each being capable of being conditioned by first, second or third selected sub-audio tones so that either all receivers, or only a select group of all of the receivers or only an intended group are the receivers accept the transmitted audio signal, there being as many selectable second sub-audio signals as there are groups and as many selectable third sub-audio signals as there are receivers.

FIELD OF THE INVENTION

The present invention relates to communication systems.

BACKGROUND OF THE INVENTION

The invention arose from a problem in coaching swimmers. A swimmingcoach watches his swimmers from a pool surround and yells hisinstructions. Swimming pools especially when indoors are noisy placesand it is difficult for any swimmer to understand the shoutedinstructions. Normally there are many swimmers being coached at the sametime and thus each swimmer has to listen for any instruction which mightbe meant for him and ignore instructions meant for any one else; this isdistracting to the swimmer.

The invention is not however limited to swimming instruction but isapplicable to most sports and other communication.

The present invention aims to provide a communication system for thetransmission of instructions from an instructor to a class or othergroup of instructees.

SUMMARY OF THE PRESENT INVENTION

One aspect of the present invention provides a communication systemcomprising an instruction unit linked electro-magnetically to areceiving unit in something to be worn by an instructee.

The electro-magnetic linking can be done at audio frequency by having aloop surrounding the class or group or by radio transmission. If radiotransmission is used, the transmitter should be of low power say 1 wattof radiated power to avoid too large an area in which the signal can bereceived.

The system can incorporate an encryption or scrambling device to preventoutsiders eavesdropping on the instructions given. There is keen rivalrybetween swimming coaches.

The system can also incorporate a switching arrangement whereby anindividual and/or a sub-group and/or the entire group can be addressedso the instructor can give instructions to whichever individual heselects, to whichever of a number of pre-selected sub-groups he chosesand/or the entire group. It would of course be possible to arrange for aplurality of individuals to be instructed without the need fordetermining in advance which sub-group they belonged to.

The receiving unit has to include an audio-transducer to produce thesound. This audio-transducer can be in the form of ear-piece to bereceived in the instructee's ear; this has an advantage in that thepower demanded from the unit is low but it is difficult to render such atransducer water-proof in a swimming environment. It is preferred in aswimming environment to use a transducer which is enclosed in awater-tight case and then to incorporate that case in the latex of aswimming cap, which in the case of a swimmer or diver would be the saidsomething worn. In a non-watery environment, the said something could bein the form of a head-piece with ear-pieces to fit in the ears althoughthere is nothing to prevent said something being anything worn orcarried by the instructee.

Instead of instructions going direct from the instruction unit which canbe a hand-held unit, it would be possible to use a relay unit to augmentthe signal and the relay unit can derive power from a mains supply.

In another aspect of the invention, a swimming cap has provision forreceiving an electronic signal receiving unit.

Said provision can be in the form of a pocket or pockets into which theunit can be inserted.

A further aspect of the invention provides a swimming cap incorporatingan electronic signal receiving device. The cap can incorporate the saidreceiving unit by being made in a dipping process with the unit beingbetween two skins or by having a patch vulcanised over the unit.

The receiving unit can be made in two parts each fitting over an earwith each part containing an audio-transducer with one in additionhaving the electronic circuitry and the other a power supply.

Unfortunately it has been found that the power demand of the receivingunit and particularly that of the transducers gives an undesirably shortlife of the receiving unit when non-rechargeable batteries are used. Ithas therefore been found desirable to use rechargeable batteries. It hasalso been found desirable to switch off the unit when not in use. Toavoid the need for mechanical switches, the unit can be switched on byan electronic signal and be held on for a determined period. One way ofdoping this would be for a part of the circuit to sense when a signalwas being received and to switch off the remainder of the circuit if thesignal was not addressed to it and another would be to switch thecircuit on when a signal was applied and then switch it off only after adelay.

A yet further aspect of the invention provides a method of rechargingbatteries without direct contact by placing the batteries with acharging circuit in an alternating magnetic field with the circuitrectifying an alternating voltage derived from the field and deriving aconstant current to recharge the batteries.

It has surprisingly been found that water does not attenuate the radiofrequencies used in a prototype sufficiently to prevent the prototypebeing used in swimming coaching, indeed the prototype was effective insix foot of water that is with a trainee at the bottom of the deep endof a swimming pool which was nominally six foot deep (six foot is over1.8 meters).

The invention will now be described, by way of example, with referenceto the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a communication system according to thepresent invention for use in coaching swimmers,

FIG. 2 illustrates a variant,

FIG. 3 is a perspective view of an instruction unit,

FIG. 4 is a circuit diagram of the instruction unit,

FIG. 5 is a circuit diagram of a receiving unit

FIG. 6 shows the arrangement of cells forming a battery used in thecircuit of FIG. 5,

FIG. 7 is a view of a swimmer wearing a cap embodying the presentinvention,

FIG. 8 is a section of a detail on line VIII-VIII of FIG. 7,

FIG. 9 is a schematic section showing detail of FIG. 8,

FIG. 10 is a a view of how the receiving unit can be worn for otheruses,

FIG. 11 shows diagrammatically a recharging unit for the battery used inFIG. 5, and

FIG. 12 illustrates how the unit of FIG. 11 co-operates with circuitryconnected to the battery to charge the battery.

DESCRIPTION OF EXEMPLARY EMBODIMENT

FIG. 1 shows in block outline a communication system. A hand-heldinstruction unit 21 incorporates a key board and associated logiccircuitry 22 which will be mentioned in more detail in relation to FIG.3, a built-in micro-phone 23, a speech encoding circuit 24, amplifyingcircuitry 25, and an aerial 26 all powered by a battery 27 or mainselectricity, a rechargeable battery is preferred. A receiving unit 28comprises a battery 29, an antenna 30, radio-frequency amplifying stages31 possibly in the form of a heterodyne receiver, means 32 for detectingwhether the received signal contains a component identifying that thesignal is intended for that receiving unit, a decoding arrangement 33,an audio-stage amplifier 34 and a power supply logic circuit 35. Thetransmission frequency can be of the order of 27 MHz or 49 MHZ but isnot critical and the radiated signal has a low power of say 1 watt andis preferably frequency modulated. Depending on the supplier of thetransmitters and receiving units, there can be any reasonable number ofreceiving units associated with one instruction unit. These receivingunits would be indentical one with another except for unit-identifyingtracks (not shown) which would be processed during manufacture to give aunique identifying code and codes common to a group and to a sub-group,it is theoretically possible to have the said common codes as part ofthe unique codes (so the unique codes would be ABA, ABB, ABC etc. withthe group code A and the subgroup code AB with the receiver sensing thefinal letter and cutting off the receiver if the final letter is not theright one) and this would economise on tracks.

FIG. 2 illustrates a variant wherein instead of restricting the range byusing low power to avoid polluting the magnetic spectrum away from theinstruction area, the instruction area 36 is surrounded by an inductionloop 37 driven by a relay unit 38 which is mains powered 39 and canreceive a signal from the instruction unit 21 by extremely low-powerradio transmission or by a cable link 40.

FIGS. 3 and 4 illustrate an instruction unit. This instruction unit iscontained in a water-tight plastics material case 41 the back of whichis adapted to receive notes written on it with say a grease pencil orother marker. The circuit inside the case as shown in FIG. 4 comprises astop watch chip 42 controlled by an initiating button 43 (FIG. 3) and astop button 44 (FIG. 3), a display 45 for the stop watch, a microphone46, and audio amplifier chip 47, a battery 48, an on-off switch 49, acalling tone generator chip 50, an array of addressing buttons some 51of which are intended to summon an individual and others 52 a group ofindividuals, these buttons controlling the tone generated, a chip 52'for superimposing the output of the tone generator chip on the output ofthe audio amplifier, and a radio frequency amplifier chip 53 with itsfrequency deciding oscillator 54. The precise circuitry and componentshave not yet been finalised and so it would be misleading to givecomponents and precise circuitry. However the requirements for the stopwatch chip are that preferably it is of a type that not only has aninitiating and a stop button but also has an arming button 55 permittingthe timing to start on a receipt of a large signal on line 56 from themicrophone denoting arrival of a loud noise such as a start-race signal.The calling tone generator can be in the form of a micro-processor whichcould not only synthesise the tones but perhaps could without too muchcost allow the buttons 52 to cover variable groups of individuals by aprogram which included a step that pushing a button 52 followed shortlyby pushing buttons 51 meant that that button 52 thereafter meant thepushed buttons 51 and then cycle the tones between the codes for theright buttons 51; the receiver unit presently developed relies on eachbutton 51 or 52 having a distinct tone and so is tuned to two tones ormore. The output of the chip 53 is fed through a rubber covered aerial26. FIG. 5 is a circuit diagram of a receiving unit. Whilst developmentis not complete and no provision has been made for scrambling thesignals as indeed was the case in FIG. 4, development has proceeded farenough to give fuller details. The antenna 30 which can be in the formof a pick-up loop passes the incoming signal through a filter 60 such asa Ceramic Murata SFE49 to a radio-frequency amplifying chip 61 such as aMulland TDA TO21 with a beat oscillator 62 controller by a 49.80Megahertz crystal oscillator 63. The output of the chip 61 is fed to atone sensing chip 64 such as a CML FX335SLVI through a noise eliminatingfilter 65. With the chip 64 there are associated a frequency-standardoscillator 66 such as a 1 MegaHertz crystal and a succession ofbreakable links 67 to determine the tones to be sensed. The output ofthe chip 64 which is the output of the chip 61 only when the correcttone is sensed is fed through amplifier stages 68 to an audio transducerarrangement 69. Another output from the chip 64 is taken to a powerswitching chip (such as a 74HC02) 69' which receives a voltage from abattery 70 and switches that voltage off or on (`on` means to the restof the circuitry direct or through a voltage regulator 71). This chip isswitched into one state by a signal from the chip 64 or a large signaltaken from the antenna 30 on line 72 and this state is the one passingthe voltage. This chip 69' is held in that state until the state isreversed by another chip 73 such as a 74HC4060 which is a counter timersetting a delay of say 30 minutes. The signal on the line 72 will onlybe large if the antenna is very close to the transmitter and so this isused to set the receiver unit functioning at the start of a trainingsession and thereafter this signal will be weak and only the signal fromthe chip 64 (which has been switched on) will operate the chip 69'.

FIG. 6 shows an arrangement of cells 80 forming the battery 70 of FIG.5. Seven miniature nickel-cadmium cells packed six around a central onewith suitable connections to arrange them in series can provide 8.40volts with a capacity of 60 milliampere-hours within a diameter of 5 cm.and a depth of 6 mm. even when the cells are encapsulated in awater-proofing plastics material.

FIGS. 7 to 9 illustrate the mechanical arrangement of the receivingunit. FIG. 7 shows a swimmer wearing a bathing cap 82 which has aprojection 83 over each ear. FIG. 8 shows that each projection containsa part 84 embodied in the cap as by the parts with a stretchableelectric interconnection 87 being attached to a layer 85 formed by afirst moulding dip with a second layer 86 being formed over the firstlayer and the parts and interconnection by a second moulding dip. Eachof the parts 84 contains an audio transducer 88 such as of Muratapiezoelectric material and forming part of the arrangement 69 with eachpart being contained in a sealed enslosure 89. The walls of theenclosure are spaced from the transducer on all sides and there is freespace behind the transducer to receive in one part the battery 70 and inthe other part a printed circuit board 90 mounting the circuitry of FIG.5 which board is about the same size as the battery (this is facilitatedby using surface mounted components), and the antenna 30.

FIG. 10 illustrates that the receiving unit can be mounted otherwisethan in a swimming cap for other uses. FIG. 10 actually shows thereceiving unit in a sweat band for foot sports with the receiving unitbeing in one or two parts. It is not essential to use rechargeablebatteries in uses where water-proofing is not a key issue. In usesdemanding head protection, the receiving unit can be incorporated in ahelmet.

FIGS. 11 and 12 illustrate a way of recharging the battery 70 withoutremoving, or obtaining direct contact with, it so it can remain sealedwithin the enclosures for the life of a swimming cap. The caps ofseveral swimmers can be thrown into a non-metallic container 91surrounded by a coil 92 in series with a capacitor 93, the coil and thecapacitor being resonant at a frequency of say 25 kiloHertz. Anoscillator 94 resonating at this frequency such as a Levell TH150 DMfeeds a power amplifier 95 such as a GA28F Mosfet powered by a powersupply unit 96 such as a Farnell LT30.2 which in turn keeps the coil 92strongly resonating. The resulting magnetic field is picked up by a coil97 in FIG. 12 which can be the aerial or antenna 30. This coil is thenconnected to a current regulating device 98 consisting of a referenceZener diode 99, resistors 100 and a transistor 101 to charge the batteryat a constant low current. The orientation of the coil 97 does not seemcritical within a wide range of orientations.

No provision has been made in the described embodiments for avoidingeaves-dropping but this would seem to be a mere matter of incorporatingcommercially available scrambling chips in the circuits.

The radio-frequency used depends largely on the licensing authoritiesallocating frequencies and their restrictions on power outputs atpermissible frequencies. Thus in the U.K., theauthorities will onlypermit minimal power at 49 MHz and so 27 MHz when they will permit 4watts will be better.

It is possible to use independent receiving units for each ear when itis desired to use two earpieces with each unit being self-contained withits own battery and circuitry. This avoids the need for a stretchableelectrical connection which even with connection anchorages may be asource of failure if the wearer uses the projections 83 as an aid inpulling a swimming cap on. It is not thought that the connection wouldbe a source of weakness and it would only be necessary in any event towind the connection around the enclosure to give a firm anchorage takingany strain off the connection's terminations.

We claim:
 1. A communication system for instructing individual membersof a group and the group as a whole comprising a transmitter to be usedby the instructor and a receiver for each memeber of the group whichreceiver contains an electric battery and is mounted on an elasticallyextensible article to be worn on the head of the respective member, eachreceiver designed to be extensible and to be contained within theextensible article, an input amplifier stabilized by a crystaloscillator and yielding an audio frequency signal, decoding means forsensing a sub-audible tone in that signal identifying that the signal isintended for the entire group or another sub-audible tone identifyingthat the signal is intended for the particular receiver, an outputcircuit for passing the signal to audio transducers, one over each earof the member in use, when the decoding means yields a signal denotingthat a sub-audible tone acceptable to that receiver is contained in theaudio frequency signal, and in that the transmitter injects asub-audible continuous tone under the control of the instructer toidentify the member to be instructed onto the audio input to thereceiver.
 2. A communication system according to claim 1 wherein eachreceiver contains a timing unit which is arranged to operate after adelay to shut off the receiver.
 3. A communication system according toclaim 1 or claim 2 wherein each receiver's battery consists of at leastone rechargeable cell and wherein each receiver contains circuitry forrecharging the battery without the battery being removable from thereceiver.